A MOLECULAR AND PHENOTYPIC ANALYSIS OF NODULARIA (CYANOBACTERIA) FROM THE BALTIC SEA

The filamentous diazotrophic cyanobacterium Nodularia forms water blooms each year in the Baltic Sea. Filaments isolated from such water blooms vary in their trichome width, degree of coiling, and properties of their gas vesicles; previously, these characters have been used to classify individuals to species level. To test the validity of such a phenotypic classification, we determined the nucleotide sequences for a region of the phycocyanin locus that includes a noncoding intergenic spacer (PC-IGS), the IGS between two adjacent copies of the gvpA gene (which encodes the main structural gas vesicle protein) and the rDNA internal transcribed spacer (rDNA-ITS), for 13 clonal Nodularia isolates from the Baltic Sea during August 1994. The complete 16S-rDNA sequence was determined for three isolates and was found to be identical in each of them. Molecular sequences for noncoding regions of the genome were used to assign isolates to three groups on the basis of PC-IGS, two groups on the basis of gvpA -IGS, and three groups on the basis of rDNA-ITS. No consistent correlation was found between genotype and any of the phenotypic features examined, and no link was found between any of these features themselves, indicating that these characters are not useful for placing Nodularia isolates into meaningful taxonomic groups. The PC-IGS, gvpA -IGS, and rDNA-ITS genotypic groupings were not congruent. This might indicate that gene flow occurs between individuals in Nodularia populations.     

REPRODUCTIVE SUCCESS OF FUCUS VESICULOSUS (PHAEOPHYCEAE) IN THE BALTIC SEA

Marine organisms colonizing brackish habitats such as the Baltic Sea must cope with the negative effects of low salinities on reproductive success because these may reduce gamete viability and/or increase polyspermy. Reproductive characteristics of the marine seaweed Fucus vesiculosus L. were studied in several brackish habitats, particularly in the northern Baltic Sea, to understand its ability to reproduce where few other marine species survive. Polyspermy and fertilization success were variable at the boundary of the continuous distribution of F. vesiculosus in the Baltic Sea, and polyspermy was high (10%–30%) when fertilization was successful. A strong female bias (80%–86%, ca. 5.5:1) was found at the northernmost limit of Baltic F. vesiculosus. Electrophysiological studies showed that many eggs have a high input resistance (519 ± 150 MΩ[mean ± SE, n = 14] at Drivan, 1995), which may be helpful in preventing polyspermy in this brackish habitat. The polyspermy block remains sodium-dependent in the northern Baltic. Sperm bound quickly to northern Baltic eggs in natural water, but fertilization was delayed compared to marine F. vesiculosus. A subset of northern Baltic eggs studied during an optimal reproductive period (7–11 July 1995) had a membrane potential (E_m) of ca. −100 mV and an effective fertilization potential (FP) of ca. 2 min with a plateau of −25 mV, but repolarized too rapidly for the FP to be protective. Pronuclear migration and cell wall secretion occurred more slowly in Baltic than in marine zygotes. The reproductive success of theseboundary populations may be dependent upon windows of opportunity when there are favorable combinations of the levels of salinity, water motion, population density, and sex ratio. These factors and the short duration of the reproductive season in the northern Baltic Sea may result in reproductive failure in some years.     

THE ASSESSMENT OF COMPETITION BETWEEN SEALS AND COMMERCIAL FISHERIES IN THE NORTH SEA AND THE ANTARCTIC1

Most of the exploited fish stocks in the North Sea are also used as a food supply by a number of seal species; the same is true for some fish and invertebrate stocks in the Antarctic—although the fisheries there are, at present, much smaller than those in the North Sea. The information needed for a critical assessment of such interactions is reviewed. Using existing techniques it is possible to estimate the quantity and size-classes of each fish or invertebrate species consumed by seals and to compare this with the commercial catch. If fishing mortality is known, these estimates can be used to calculate the level of mortality imposed by the seals. However, a realistic evaluation requires information on the distribution and movements of the fish, the seals' feeding effort, and the fisheries effort in time and space. At present it is difficult or impossible to obtain this information, but recent technological developments in telemetry equipment will soon make it feasible. To assess the economic effects of changes in seal numbers on the fishery, or the ecological effects of changes in fisheries effort on seal populations, requires additional information on the responses of the fishery and the seals to changes in fish abundance, and of the commercial market to changes in the supply of fish.     

ALLOXANTHIN IN DINOPHYSIS NORVEGICA (DINOPHYSIALES, DINOPHYCEAE) FROM THE BALTIC SEA

The pigment composition of Dinophysis norvegica Ehrenberg from the central Baltic Sea differs from the normal pigment pattern found in dinoflagellates, which contain peridinin as a typical marker pigment. In D. norvegica isolated by cell fractionation of field samples, the major carotenoid was alloxanthin, a typical cryptomonad pigment. No evidence was found that the presence of alloxanthin was due to a recent phagotrophic uptake of cryptomonads, so the presence of alloxanthin in D. norvegica may be a consistent feature of a permanent endosymbiosis.     

寰椎的测量、相关与性别判别分析

本文对85例(男46,女39)国人寰椎进行了四项测量,其性差均非常显著,但两性重迭率≥38.9％。另算出两项指数,其性差不显著。从中挑选全宽(X_1)和矢径(X_2)两个变量经计算得判别式Z=X_1+2.21098x_2,临界值Z_0=172.9102。经组内外回代误判率分别为18.5％和12.9％。对四项测量作了相关分析,其中寰椎矢径与椎孔横径、全宽与椎孔矢径均呈中度正相关。并用寰椎矢径(X_2)推算椎孔横径(y),其男性Y=18.01±0.2579X_2,女性Y=4.88±0.5505X_2。     

陕北延长群一新古鳕类及其生物地层意义

本文记述了在陕西北部耀县铜川组发现的古鳕科一新属、种——延长三叠鳕(Triassodusyanchangensis,gen.et sp.nov.)。在对其形态特征作较详细描述的基础上,认为它既与美国晚三叠世的吐鲁瑟欧鳕(Turseodus)很接近,又与我国四川须家河组(晚三叠世)的蜀鳕(Sh-uniscus)相似。基于上述的理由,认为铜川组的时代是晚三叠世。根据迄今在我国晓三叠世发现的鱼类,探讨了我国晚三叠世的鱼群与北美的关系。     

RESTING CYST FORMATION OF EUTREPTIELLA GYMNASTICA (EUGLENOPHYCEAE) IN THE NORTHERN COASTAL BALTIC SEA1

Resting cyst formation of Eutreptiella gymnastica Throndsen was observed during a mesocosm experiment, where nutrient enrichment had induced almost a unialgal bloom. Cells and resting cysts of E. gymnastica were examined in scanning (SEM) and transmission electron microscopy (TEM) and light microscopy. Mature cysts were spherical, with a smooth thick mucilaginous cover that appeared layered when observed with the TEM. Intermediate forms were spherical and lacking flagella and a mucilaginous cover; the euglenoid pellicular striation and canal opening were easily visible. The volume of these intermediate spherical cells and mature cysts was estimated to have increased threefold compared to flagellated cells and contained many paramylon grains. When the cells were grazed by zooplankton, the paramylon grains passed the gut intact and were packed into fecal pellets. Intact undigested paramylon grains were observed in SEM after the breaking up of the pellets.     

PIGMENTS OF THE RETINA : II. SEA ROBIN,SEA BASS,AND SCUP

1. Visual purple from the sea robin, sea bass, and scup is almost identical spectroscopically with that from frogs. The interrelations of this pigment with vitamin A and retinene are also the same as in the frog. 2. In strong acids or at pH > 11, the visual yellow of sea robin retinas is converted irreversibly into a pH indicator, yellow in acid and almost colorless in alkaline solution. Unlike neutral visual yellow, the indicator is not removed to form either vitamin A or visual purple. In the ammoniacal retina the reversion of visual yellow itself to purple is accelerated. 3. The combined pigment epithelium and choroid layer in these fishes contain vitamin A, flavine, and an unidentified xanthophyll.     

FIRST REPORT OF GYMNODINIUM PULCHELLUM (DINOPHYCEAE) IN NORTH AMERICA AND ASSOCIATED FISH KILLS IN THE INDIAN RIVER, FLORIDA

Fish and invertebrate kills were reported from September to October 1996 in the Indian River, Florida, coincident with blooms of the dinoflagellate Gymnodinium pulchellum Larsen 1994. This is the first report of a bloom of this species in the Americas. Fish and invertebrate species affected were common snook ( Centropomus undecimalis ), striped mullet ( Mugil cephalus ), hardhead catfish ( Arius felis ), red drum ( Sciaenops ocellatus ), sheepshead ( Archosargus probatocephalus ), black drum ( Pogonias cromis ), blue crab ( Callinectes sapidus ), and shrimp ( Penaeus spp.). However, Gymnodinium pulchellum has previously caused fish kills in Japan and Australia. Examination of archived phytoplankton samples from a fish kill reported in the same area of the Indian River in August 1990 confirmed the presence of high concentrations of G. pulchellum. Fish kills associated with Alexandrium monilatum and potentially Pfiesteria -like species in the Indian River also are discussed. Scanning electron microscopy provided additional morphological detail on this distinct but little-known dinoflagellate.